The invention relates to a displacer for low-temperature refrigerating machines comprising a regenerator disposed in a hollow space of the displacer.
Low-temperature refrigerating machines are cooling equipment in which thermodynamic cycles operate. (See, for example, U.S. Pat. No. 2,906,101.) A single-stage low-temperature refrigerating machine essentially comprises a chamber with a displacer. The chamber is alternately connected in a given manner to a high-pressure gas source and a low-pressure gas source, with the thermodynamic cycle (Stirling cycle, McMahon/Gifford cycle, etc.) operating during the reciprocating motion of the displacer. The working gas neon cryogenic fluid may be carried in a closed cycle. As a result, heat is abstracted from a given region of the chamber. With two-stage refrigerating machines of this type and helium as the working gas temperatures down to 10.degree. K. and lower can be produced.
An essential component of a low-temperature refrigerating machine is the regenerator through which the working gas flows before and after expansion. It is known to locate the regenerator within the cylindrical displacer. In this case, the regenerator must have good heat-storing properties in order that a sufficiently high heat exchange may take place between the working gas and the regenerator. Moreover, the displacer as a whole must then be a poor heat conductor as otherwise the heat abstracted from one side of the chamber is quickly replaced through thermal conduction. Known regenerator materials are bronze or lead spheres, bronze wool and bronze gauze.
A drawback of displacers comprising these regenerator materials is that their overall manufacture is expensive and complicated. When the regenerator material consists of spheres, gas-permeable caps or grids must be provided to prevent the spheres from dropping out. Bronze gauze is expensive and difficult to introduce into the hollow interior of the displacer. Bronze wool poses much the same problem as spheres. No part thereof may be allowed to get out as otherwise the chamber walls might be damaged.